The tentacles aren't mine, they're just a revised version of TOPS', and spriting more like them from scratch and adding them to other animations is going to be a massive royal bitch that I won't know if I'm capable of until I try it...
What you see here are more or less my first sprites, I've done other things here and there but not full animations, my approach is to learn as I go and do the things I know I can do first and get better along the way. So all that's here right now is with Radel as a base with very little changes to the outline (slightly shortened, custom feet and head, upper arms slimmed a little), and when I exhaust the frames I can do that to that'll look good, I'm gonna move on to frankenspriting, and then to tentacle attacks with bases, and then finally to the scratch ones I'll have to add to all his non-attack animations.
At the moment I don't have a goddamn clue how to do that, but like with everything else, I expect to figure it out when I get there. I went from not knowing how to sprite to this, so I'm not gonna let a silly thing like that stop me.
Anyway, to answer the question you actually asked (and this is also TOPS' trick but I REALLY like it and will use it elsewhere), the body and the tentacles animate differently. The body has 4 frames, the tentacles have 8. The full stance is 16.
It works like this:
Body: 1 1 2 2 3 3 4 4 4 4 3 3 2 2 1 1
Tentacles: 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
If that makes sense. :)
Expect similar tricks for Catwoman and other Lasher animations. :)
By the way, I'm pretty confident in the other animations, but I still need to tweak the stance again at some point. He does need head motion after all, I think, and I can do better on the abs now. The weird gap there is like a pixel too large. [/perfectionist]
EDIT: Bonus fun fact: His legs and body work the same way in his back walk, with minor changes to the legs because it's a different one in the foreground/background.
Body: 1 2 3 4 5 4 3 2
Legs: 1 2 3 4 1 2 3 4
Rinse and repeat and tweak for neat effects and time-saving. :P